This invention relates to drill guides for use in corticotomy procedures to guide a drill bit into the cortex of a bone.
Since the early 1950s, there has existed a procedure for effective limb lengthening which involves circumferential severance of the cortex of the bone to be lengthened and gradual separation of the separated cortex ends as new bone is generated in the distraction gap. An important step to the procedure is the performance of the corticotomy procedure wherein the cortex is circumferentially severed. It is important to the corticotomy procedure that damage to the endosteum and the periosteum be minimized. These membranes are important to the regeneration of the cortex, and hence to the bone lengthening or transporting process.
Heretofore, corticotomy procedures have been performed through the use of osteotomes, power saws, and drills. Using an osteotome, the corticotomy is performed by making an incision through the periosteum and inserting a periosteal elevator medially and laterally to elevate the periosteum. An osteotome is inserted into the rent in the periosteum to cut a groove in the cortex. Care is normally taken by the surgeon not to penetrate the medullary cavity or the endosteum membrane surrounding it. Employing the osteotome, the surgeon is able to make a circumferential severance of the cortex. This procedure is explained in U.S. Pat. No. 4,881,534 issued to Uhl et al. on Nov. 21, 1989.
Reciprocating or oscillating power saws and power osteotomes have also been employed in corticotomy procedures following substantially the same procedure as described above. The principal advantage of such power devices is that they require less effort by the surgeon. However, power devices tend to slip, causing injury to the periosteum or endosteum. An example of a power device is found in the Warfield et al. U.S. Pat. No. 3,678,934 issued Jul. 25, 1972.
Manual and power drills have also been used to bore into the cortex to form a circumferential region of weakened cortex which may be broken and removed. By carefully and repeatedly boring the drill into the cortex at different angles and different depths, a circumferential severance of the cortex may be accomplished. However, a difficulty with drilling is that there has been no effective means for guiding the drill bit to accurately locate the drill position for the different angles and to reduce likelihood of damage to the periosteum and endosteum.